Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters
(ΔGo, ΔH, ΔS) for the formation of the citrate complexes with the Mn2+, Co2+, Ni2+ and Zn2+ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic
strength of 100 mM was maintained with NaClO4. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes
have been discussed.
Authors:D. Wyrzykowski, D. Zarzeczańska, D. Jacewicz, and L. Chmurzyński
Isothermal titration calorimetry (ITC) and potentiometric titration methods have been used to study the process of proton transfer in the copper(II) ion-glycylglycine reaction. The stoichiometry, conditional stability constants, and thermodynamic parameters (ΔG, ΔH, and ΔS) for the complexation reaction were determined using the ITC method. The measurements were carried out at 298.15 K in solutions with a pH of 6 and the ionic strength maintained with 100 mM NaClO4. Carrying out the measurements in buffer solutions of equal pH but different enthalpies of ionization of its components (Mes, Pipes, Cacodylate) enabled determination of the enthalpy of complex formation, independent of the enthalpy of buffer ionization. The number of protons released by glycylglycine on account of complexation of the copper(II) ions was determined from calorimetric and potentiometric measurements.
Authors:D. Wyrzykowski, J. Czupryniak, T. Ossowski, and L. Chmurzyński
By using the isothermal titration calorimetry (ITC) technique, thermodynamic parameters have been determined for reactions
of the Mg2+, Ca2+, Sr2+, and Ba2+ ions with the citrate anion. The measurements were run in the Cacodylate, Pipes and Mes buffer solutions of a pH of 6, at
298.15 K, as well as in the Tricine, Tapso, and Tris–HCl buffer solutions of a pH of 8. Further, based on the results of potentiometric
titration, the conditional stability constants were determined for the citrate complexes at both pH values. The effect of
the reaction environment and the metal ion identity on the interaction energy with the citrate ligand and the stability of
the resulting compounds have been discussed.
Authors:D. Wyrzykowski, E. Hebanowska, G. Nowak-Wiczk, M. Makowski, and L. Chmurzyński
Thermal decomposition of citric acid, trans- and cis-aconitic acid has been studied using the TG-MS, TG-FTIR and DSC techniques. The measurements were carried out in an argon atmosphere over a temperature range of 293–673 K. The influence of the acid structures and configurational geometry on stability of the transition products and pathways of thermal transformations of the studied compounds studied is discussed.